Apparatus employing horizontally elongated carbon arc sources



July 21, 1959 s. M. SEGAL 2,896,103

APPARATUS EMPLOYING HORIZONTALLY ELONGATED CARBON ARC SOURCES Filed Jan.51, 1957 3 Sheets-Sheet 1 mmvroa.

ffmZe/fjal July 21, 1959 s. M. SEGAL 2,896,108 APPARATUS EMPLOYINGHORIZONTAL-LY ELONGATED CARBON ARC SOURCES Filed Jan. 31, 1957 3Sheets-Sheet 2 INVENTOR. Sianlg M5 aZ BYW h S. M. SEGAL APPARATUSEMPLOYING HORIZONTAL-LY ELONGATED CARBON ARC SOURCES Filed Jan. 31, 19573 Sheets-Sheet 3 INVENTOR.

5547226 M 5 aZ United States Patent APPARATUS EMPLOYING HORIZONTALLYELONGATED CARBON ARC SOURCES Stanley M. Sega], Springfield, Va.Application January 31, 1957, Serial No. 637,583

8 Claims. (Cl. 314-47) (Granted under Title 35, US. Code (1952), see.266) The invention described herein may be manufactured and used by orfor the Government for governmental purposes without the payment of anyroyalty thereon.

This invention relates to illuminating sources and more particularly toa structure employing a horizontally elongated carbon electrode andapparatus facilitating the use of such carbon electrodes in Searchlightand floodlight equipment. The structure herein described permitsrealizing the advantages of the principles and structure taught by theinstant invention for military and commercial applications.

Present carbon arc searchlights use a round source. The beam is a narrowcone. To spread the beam, the source, usually used in conjunction with aparabolic reflector, is moved out of focus. An alternative method is touse spread lenses in the front window of the searchlight. Either ofthese two methods spreads the beam with a very large percentagereduction in beam candlepower. By using a rectangular source, such as inthe instant invention, the spread beam is realized Withoct any loss inbeam candlepower due to forming the light source by the use of thebrighter electrode crater rather than an arc stream. The ratio of thehorizontal to vertical dimensions of the horizontally elongated carbondepends on the particular application. For a very wide spread beam, theextremities of the source would be out of focus in which case aspherical instead of a parabolic reflector could be used in conjunctionwith a correcting front window.

Experimentation with horizontally elongated positive carbon electrodeshas shown that the use of a single negative electrode will cut deepconcave curves or craters in the positive electrode after short periodsof operation, from 30 seconds to 2 minutes. The curves and craters aredue to more rapid burning or evaporation in the areas on which theelectron stream impinges. If an elongated negative electrode is used thenegative foot-point, or point on the electrode from which the stream ofelectrons leaves, will slide along and slip off an elongated negativeelectrode. If the negaitve footpoint is kept stationary by some specialmeans, such as.

magnetic fields, etc., the elongated negative electrode would thenfunction like the conventional electrode. Whether an elongated negativeelectrode is used or the negative foot-point is controlled, the streamof electrons will only leave the negative electrode from a small spotcausing uneven conscmption of a positive electrode that has an elongatedcross-section.

It was discovered that the uneven burning could be overcome by the useof a plurality of negative electrodes and that concave, straight orconvex burning ends could be maintained as desired by operating withpredetermined horizontal angles with respect to the longitudinal axis ofthe positive electrode. Zero'degrees appears to be the optimum verticalangle. It was further discovered that the whole rectangularcross-section of a horizontally elongated carbon electrode could beignited ice with even brilliance and quiet operation by selection ofproper are parameters, such as arc length, voltage, cur rent andnegative electrode angle.

It is a primary object of the present invention to pro vide a carbon arcsource with a substantial horizontal elongation.

It is a further object of the present invention to pro vide a lightsource for producing horizontally elongated beams of light of highbrightness and high infrared intensity per unit area without beamdistortion.

It is a further object of the present invention to provide a lightsource employing horizontally elongated carbon electrodes for producinghorizontally elongated beams of light of uniform beam candlepowerwithout beam distortion.

It is a further object of the present invention to provide a lightsource employing a horizontally elongated positive carbon electrodewhich operates with uniform brightness per unit area.

It is another object of the present invention to pro vide a carbon arcsource employing a horizontally elongated positive carbon electrodewherein the positive electrode consumption may be controlled.

It is a still further object of the present invention to provide acarbon arc source employing a horizontally elongated positive carbonelectrode wherein end burning of the positive electrode may becontrolled to produce a desired configuration.

It is another object of the present invention to provide a carbon arcsource employing a horizontally elongated positive carbon electrode anda plurality of negative electrodes to produce uniform burning andbrightcarbon electrodes of ness per unit area of the positive electrode.

It is a further object of the present invention to provide a carbon arcsource employing a horizontally elongated positive carbon electrode anda plurality of negative electrodes adjustable in horizontal anglerelative to the positive electrode to provide controlled consumption ofthe positive electrode.

- It is also an object of the present invention to provide horizontallyelongated carbon electrodes having a high ratio of length to width.

It is also an object of the present invention to provide horizontallyelongated carbon electrodes for high and low current operation.

It is a further object to provide horizontally elongated predeterminedspectral characteristics.

These and other objects will become apparent as the description proceedswherein- Fig. 1 shows a section through a-solid horizontally elongatedcarbon electrode;

Fig. 2 shows a section through a solid horizontally elongated carbonelectrode with tapered ends;

Fig. 3 shows a section through a cored horizontally I elongated carbonelectrode;

Fig. 4 shows a section through a cored horizontally elongated carbonelectrode with tapered ends;

Fig. 5 is a diagram of one form of circuit to provide independentenergization of each of-a plurality of carbon electrodes;

7 mechanism;

Fig. 8 is an elevational view, partly in section, of a vertical angleadjustment mechanism; Fig. 9 is a view taken on the line 99 of Fig. 7; vf a F sl avview kt .onthe li en-. 10 of Fig. 7; g;

resistors and ditficulty in striking the arc.

Fig. 11 is a vertical section taken on the line 11:11 of Fig. 7;

Fig. 12 is a vertical section taken on the line 12-12 QfEig- 7; i V V-Fig. 13 is a plan view of a motor-driventype of negative electrodeholder mounted for horizontal angle dj ment;

Fig. 14 is n elevational of Fig. 13;

Fig. 15 is a perspective View of ahorizontal angular adjustment devicefor the motor-driven type of negative electrode holder shown in Fig. 13;and

Fig. 16 is a vertical section taken on the line 16-16 of Fig. 15.Reference is now made to Figs, l-4 showing two configurations ofhorizontally elongated positive carbon electrodes. Various ratios of thehorizontal to vertical dimensions of horizontally elongated positivecarbon electrodes were tried, such as 32 mm. x 3 mm, 32 mm. x 6 mm, 1inch x A; inch and 1 inch x A inch.

The conventional mercury capillary arc source measures 25.5 mm. x 1.5mm. Thernercury capillary arc source is satisfactory for certainapplications but fails in brightness and spectral characteristics forother applica tions and exhibits too narrow a vertical beam spread forcertain applications.

In general, if the ratio is unity a single negative electrode isadvisable and as the ratio increases the number of negative electrodesincreases. In a particular application in which the ratio was 621, twonegative electrodes were used. With rectangular carbon electrodes 1 and2 as in Figs. 1 and 3, respectively, plural negative electrodes are usedto assure uniform consumption of the positive electrode and unformbrightness. In order to overcome the rapid central evaporation ofrectangular electrodes when using a single negative electrode, taperedpositive electrodes, such as 3 and 4, in Figs. 2 and 4, respectively,were used. It was found that the tapered or oval positive electrodes 3and 4 would operate with a single negative electrode but only withmarginal improvement over a rectangular electrode using a singlenegative.

As previously discussed, it may be desirable to mainview taken on theline 14-14 'tain straight, concave or convex burning ends on thepositive carbon by varying the horizontal angle of the individualnegative electrodes relative to the positive carbon electrode by meanswhich will be more fully described hereinafter.

Certain ditficulties may arise when using plural negative electrodessuch as the need for individual ballasts or Further, a simultaneousstrike may draw too much current and with successive strikes the secondstrike may extinguish the first are by a momentary drain on the totalcurrent and sudden unbalance in magnetic fields for operating the arc.Also, even though both negatives are conducting, there may be a tendencyfor the arc of one negative to combine with the arc of the other beforeapproaching the anode or positive electrode. These difficulties may allbe overcome by proper selection of are parameters such as arc length,voltage, current and negative electrode angle.

Positive horizontally elongated carbon electrodes can be operated athigh current when constructed with a thin outer Shell and special corematerial 5, such as shown in Figs. 3 and 4, or at low current whenconstructed of solid carbon with small stabilizing cores 6 as shown inFigs. 1 and 2, made of ground carbon formed into a mastic. The solidcarbon of the positive electrodes has the same com.- position as isfound in commercially available conventional carbons. The cored varietymay be made by cutting slots in solid blanks -or molded in the desiredhollow form. The core material 6 is made of ground carbon and maycontain an alkali salt in small amounts to which water is added to 01 1amastic. The cored electrodes are the easiest to operate. Special corematerials with .a thin shell maybe composed in many different waysdepending on the type of spectral characteristic desired. For example,cores 5 of positive electrodes giving a bluish-white light would containsalts of the metals of the cerium group, such as cerium oxide and ceriumfluoride; for a more reddish light, iron or strontium may be used. Theparticular composition of the cores is well understood in the art andforms no part of the present invention otherthan that such cores areused in the horizontally elongated carbon electrodes of the presentinvention.

Figs. 5 and 6 show circuit arrangements which may be used for the arcsources made in accordance with the instant invention. The pluralnegative electrodes 7 in Fig. 5 may be operated to ignite thehorizontally elongated positive carbon electrode 8 with separateballasts or resistors 9 for eachnegative electrode or a single ballast11, asin Fig. 6, for both negative electrodes. In the circuitarrangement of Fig. 5, the total current flow from the direct-currentsource 12 divides evenly between the dual negative electrodes 7 so theywill operate simultaneously. The current division may vary slightly dueto are conditions. If one negative electrode fails to func tion, thecurrent in the remaining negative electrode path will not increase. Itis possible to modify the source 12 so that the voltage is alternatelyapplied to each electrode so that the negative electrodes 7 willalternate in operation. The circuit arrangement of Fig. 6, includingdirect current source 12', permits such alternate operation of negativeelectrodes 13 to ignite the positive electrode 20, which may berectangular rather than tapered as shown, by the use of magnetic fieldsproduced by current flow in the coils 10, 10 which causes the arc toalternate between the negative electrodes 13. While direct currentsources have been discussed and shown in Figs. 5 and 6, it is possibleto use alternating current sources to energize the arc source. Thealternate operation as in Fig. 6 results from alternating increase incurrent flow in each of the coils 10, 10 due to the reduction inresistance in each negative electrode path when the arc is struckcausing greater current flow in the corresponding magnetic circuit whichin turn repels the arc and blows it to the other negative electrodewhich then increases the current in its corresponding magnetic circuitand reverses the cycle. The are is thus caused to alternate between eachnegative electrode and the positive electrode.

Photometric measurements were made to determine the distribution ofintensity per unit area in the visible and the near infrared spectrumrange. Tungsten ribbon opcrating at a color temperature of 2870 degreesK. was used as a reference. Longitudinal brightness of a horizontal'lyelongated solid carbon electrode 32 mm. x 6 mm. operating with dualelectrodes carrying a total current Qf'140-amperes was 180 candles/sq.mm. or 25 times brighter than tungsten ribbon operating at a colortemperature of 2870 degrees K., 14 times brighter than tungsten wireoperating at a color temperature of 3100 degrees K., 9 timesbrighter'than tungsten wire operating at a color temperature of 3300degrees K. and better than 3 times brighter than tungsten wire meltingat a color temperature of3817 degrees K.

A watcr cooled high intensity 32 mm. X 6 mm. cored horizontallyelongated positive carbon electrode showed a brightness of 100.0candles/ sq. mm. over a 16 mm. longitudinal scan when operated at.240amperes with a single negative electrode. A longitudinal brightness of600 candles/sq. mm. was obtained at the center of this electrode withdual negatives operating at amperes. The brightness tapered off oneither side of the center to about 0 candles/sq. mm. a few mm. from eachend. By proper negative electrode angle adjustment uniform or irregularlongitudinal brightness distributions may be obtained.

The ira e int nsitvper area of a 32 mm. x 6 mm. solid horizontallyelongated carbon electrode operating with dual negative electrodes and atotal current of 120 amperes was 23 times greater than that of thetungsten ribbon operating at a color temperature of 2870 degrees K.Although a cored high intensity water-cooled elongated electrodeexhibited an infrared intensity per unit area 33 times greater than thatof the tungsten ribbon operating as above, a disproportionate increasein brightness was observed which would present filter problems inapplication.

Power consumption varies over a wide range for the arcs. The lowestpower necessary to completely ignite the end of a 32 mm. wide positivecarbon was 1.8 kw. while the highest power employed was 20.8 kw.

Reference is now made to Figs. 7-12 which illustrate apparatuspermitting both vertical and horizontal angle adjustment of negativeelectrodes relative to the longitudinal axis of the positive carbonessential to control the burning of the positive electrode when usinghorizontally elongated solid or cored carbon electrodes. Each of thenegative electrodes 14 are releasably secured in a bore 15 of block 16by a thumbscrew 17. The block 16 engages a horizontal sliding bearing 18in the vertical support 19. A horizontal slot 21 extends substantiallythe length of the support 19 to permit radial movement of block 16 whichis retained in the horizontal sliding bearing 18 by a thumbscrew 22. Thevertical support 19 is mounted for sliding motion along each of thesplit fiat ring segments 23 by a bracket 24 provided with a thumbscrew25 for locking the position of the negative electrode at selected angleswith respect to the longitudinal axis of the horizontally elongatedpositive carbon electrode 26. A spring 27 extending from the thumbscrew22 to the bracket 24 retains the block 16 against the adjustable stop 28also carried in the bracket 24. A pointer 29 which cooperates with thedegree markings 30 on the split ring segments 23, is secured to theblock 16 for indicating the degree setting of the electrode on the ringsegments 23. The bell-crank lever having arms 31 and 32 is eccentricallysecured to the vertical support 19 and has one arm 32 which contacts theblock 16. It is evident that when it is desired to strike the arc thearm 31 is pushed down which causes the block 16 to be moved forwardtoward the positive electrode and when the arc is struck the arm 31 isreleased and the block 16 is drawn back by the spring 27 to a positiondetermined by the setting of the adjustable stop 28. The arm 31 must beinsulated for safety when it is hand operated. A negative electrodeholder such as described above is used for each negative electrode andas shown in Fig. 7 for dual negative electrodes, one holder is mountedon each of the two segments 23 of the split flat ring. These segments 23are mounted on the angle bracket 33 and insulated therefrom as at 34.The angle bracket 33 is in turn supported by the vertical arcuate arms35 attached to a sleeve 36 which may be adjusted vertically by means ofadjusting screw 37 on a suitable standard or support 38. Verticaladjustment of the assembly including the angle bracket 33, split ringsegments 23 and negative electrodes 14 and the holders therefor,previously described, is accomplished by means of slides 39 which rideon the arms 35. The slides 39 may be secured in fixed position on thearms 35 by clamping bolts 41. The angle bracket 33 which supports thenegative electrode holder assembly is carried by a shaft 42 extendingbetween the slides 39 by means of U-bolts 43 passing through the anglebracket 33. The ends of the shaft 42 are secured to the slides 39 in anyconvenient manner. This construction permits the negative electrodes 14to be adjusted to various vertical angles relative to the horizontallyelongated carbon electrode 26. The positive electrode 26 is supported bythe structure shown generally at 44 which may include a water-cooled orother type head. It should be understood that certain applications mayrequire a wide range of hori zontal angle and vertical angle adjustmentsnecessitating the use of a structure as described, while otherapplications may only require one specific setting of the vertical andhorizontal angle for which an appropriate structure may bedevised.Further, other variations in the struc ture,'to permit varying thehorizontal and vertical angles, may be made without departing from thebasic teachings of the instant invention.

Figs. 13-16 show another form of negative electrode holder which isdesigned to advance or retract the electrode 45 by motor driven means.The motor drive is connected to the mechanism shown generally by 46 foradvancing or retracting the negative carbon electrode 45 through aflexible or rigid shaft at 47. This mechanism 46, except for theadditional structure shown in Fig. 15, is a standard commerciallyavailable item and will therefore not be described in detail herein. Theadditional structure shown in Fig. 15 includes a base block 48 ofsuitable electrically conductive material having a slot 49 slightlylarger than the dimensions of the split ring segments 23 so that thebase block 48 may be moved freely along the split ring segments 23. Athumbscrew 51 permits clamping the base block 48 in a position along thesplit ring segments 23 depending upon the horizontal angle of thenegative electrode desired relative to the positive horizontallyelongated carbon electrode. A support block 52 of suitable electricallyconductive material is mounted on the base block 48 by a wing nut andbolt as at 53 to permit rotating the support block 52 on the base block48 for horizontal angular adjustment of the negative electrode 45. Themechanism shown generally by 46 is carried by a stud 54 threaded at oneend and having a reduced portion 55 passing through the support block 52so that when the mechanism 46 is bolted to the support block 52 it maybe freely rotated through a vertical angle which is governed by thephysical design of the components. The stud 54 has a groove 56 forretaining one end of a spring 57, the other end of which is secured to abolt 58 secured in an arm 59 of the holder mechanism 46. The arm 59 isintegral with the electrode clamp 61 through which electrical energy isconducted to the electrode 45 from the conductor 62 which is connectedto a terminal, not shown, located in the aperture 60 in support block 52and which in turn may be connected to a source of electrical energy, notshown. The outer vertical face 63 of the base block 48 bears index marks64 which cooperate with a single index line 65 on the support block 52for measuring horizontal angular adjustment of the electrode 45 relativeto the positive electrode, not shown. The degree marks 30 on the splitring segments 23 are the angles which the negative electrode 45 makeswith the longitudinal axis of the positive electrode, not shown in Figs.13-16, while the base block 48 and support block 52 combination alsopermit the negative electrode 45 to be rotated about the bolt 53 tochange the horizontal angle, as above, arc length and foot-point alongthe positive electrode, not shown. Using the degree markings 30 on thesplit ring segments 23 the locus of the center of rotation, for eachlength of negative carbon electrode, is a relatively fixed point on thelongitudinal axis of the positive horizontally elongated carbonelectrode, or fixed foot point on the positive electrode, while in thebase block and support block combination the center of rotation is atthe bolt 53. The structure shown in Fig. 15 therefore is an alternativewhen a stationary support other than the split-ring segments is used,and has the advantage of permitting changes in arc length and foot pointon the positive carbon as well as horizontal and vertical anglesmeasured as heretofore described.

Having thus described my invention, what I claim as new and wish tosecure by Letters Patent is:

1. A carbon arc device comprising in combination a positive electrodehaving an elongated cross-section, means for supporting said positiveelectrode with the length thereof normal to an exposed cross-sectionalarea,

a plurality of negative electrodes, holder means ,for. each saidnegative electrode for independently supporting each "of said pluralityof negative electrodes to project towards the exposed cross-sectionalarea 'of said positive electrode with the longitudinal axis of each saidnegative electrode angularly disposed relative to the longitudinal axis"of said positive electrode, semicircular" segmented mounting meansslidably carrying said holder means thereon, arcuate support membersextending normal to said semicircular segmented mounting means andconnected thereto for slidably adjusting said semicircular segmentedmounting means along the length of said arcuate support members forrelative vertical angular adjustment therewith, a base for supportingsaid arcuate support members, and means for electrically energizing saidpositive and negative electrodes whereby an electrical arc may beestablished.

2. A carbon arc device as recited in claim 1 wherein said holder meansfor each said negative electrode comprises an angle bracket releasablyengaging said semicircular segmented mounting means, a firstsupportnlember carried by said angle bracket including a recessextending horizontally and communicating with a hori- 'zontal slot, asecond support member slidably disposed in said recess and secured insaid slot for horizontal sliding movement along said recess within thelimits of said slot, a bore in said secondsupport member for receivingan electrode therein, a lever rotatably secured to said first supportand engaging saidsecond slidably disposed member for imparting movementto said second support member along said recess, biasingmeans opposingthe forward motion of said second support member and adjustable ,stopmeans mounted on said angle bracket and engaging said second slidablydisposed member.

3. A carbon arc device as recited in claim 1 wherein said holder meansfor each said negative electrode com prises motor driven means forcontrolling the movement of said negative electrode, a base memberhaving an opening therein for receiving said semicircular segmentedmounting means for sliding engagement therewith, a support membercarried by said base member. for relative rotation about an axis normalto said base member, stud means securing said motor driven holder tosaid support member providing vertical angular adjustment of said motordriven holder and horizontal angular adjustment about said vertical axisand biasing'means connected between said stud means and a jaw engagingsaid negative electrode on said motor driven holder to impart a clampingaction on said negative electrode and electrical conductor meansconnected between said supportmember and said jaw.

4. A carbon arc device as recited in claim 1 wherein means forenergizing said positive and negative electrodes comprises a source ofelectrical energy connected ne tes V 8 to said positive and negativeelectrodes, said negative elect odes being connected in parallel to saidenergizing sou 'ce'and each path of said parallel connection includingelectrical ballast means for limiting the current therein.

' 5. A carbon arc device as recited in claim 1 wherein said means forenergizing said positive and negative electrodes comprises a source ofelectrical energy, a plurality of serially connected electricallyconducting paths, each said conducting path including a negativeelectrode and electro-magnetically actuated arc control means, andelectrical ballast means interconnecting said plural conducting pathsand said source of electrical energy for limiting the current in saidconducting paths.

6. A carbon arc device comprising a common elec trode having anelongatedexposed cross sectional area substantially normal to its longitudinalaxis, means for supporting said common electrode, a plurality ofelongated other electrodes and means for intermittently moving andsecuring said other electrodes with their longitudinal axes in the planedetermined by the longitudinal axis of said common electrode and themajor axis of said cross sectional area and with their longitudinal axesdirected toward said cross sectional area whereby operation of said arcdevice produces an elongated light source.

7. A carbon arc device comprising a common electrode having an exposedelongated cross sectional area substantially normal to its longitudinalaxis, means for supporting said common electrode, a plurality ofelongated other electrodes and means mounting said other electrodes forsimultaneous horizontal and vertical arcuate adjustment when the deviceis'oriented with said longitudinal axis and the major axis of said crosssectional area both horizontally disposed with said other electrodescontinually pointed toward said cross sectional area at a predetermineddistance from said area. i 8. The carbon arc device of claim 7 whereinsaid other electrodes are connected to said means mounting said otherelectrodes by spring biased positioning means for permitting independentlongitudinal movement of each said other electrode toward said commonelectrode and spring driven return of each said electrode to apredetermined equilibrium position.

References Cited in the file of this patent UNITED STATES PATENTS572,312 Price Dec. 1, 1896 628,782 Faulkner July 11, 1899 881,518 WilsonMar. 10, 1908 1,007,151 Speiden Oct. 31, 1911 1,032,247 Smith July 9,1912 1,871,699 Jeppsson Aug. 16, 1932 2,156,360 Stahn May 2, 1939

